Chin tremor is an involuntary rhythmic trembling of the muscles of the lower jaw. The symptom accompanies various conditions in children and adults: parkinsonism, perinatal pathology of the central nervous system, hydrocephalus, etc. Tremor is rarely isolated, usually combined with other manifestations (cerebral, focal). Comprehensive diagnostics includes laboratory tests, tomography, neurophysiological methods. Medications are prescribed that affect the symptoms, developmental mechanisms and causes of trembling, in some cases, neurosurgical intervention is necessary.
For Parkinson's disease, rest tremor is pathognomonic, which occurs when the muscles are completely relaxed. Its development is explained by the presence of central oscillators (sources of rhythmic activity) caused by a slowly progressive degenerative process in the central nervous system. This leads to the loss of dopaminergic neurons in certain areas of the brain stem: substantia nigra, locus coeruleus, and others. But the exact reason for the change is still unknown.
Most often, parkinsonian trembling can be detected in an elderly person, the tremor of the chin, lips and limbs increases with excitement and mental stress, decreases or completely disappears with active movements, and is absent during sleep. With the course of the disease, rigidity, plastic hypertonicity, slowness of action (bradykinesia) join. Mimicry is impoverished, patients move with a shuffling gait in a hunched posture.
Isolated chin trembling or geniospasm is considered a variant of essential tremor. This is a rare hereditary disease that is transmitted in an autosomal dominant manner. Its main symptom is an intermittent tremor of the chin, which increases with emotional stress and crying.
Trembling appears in the first days after birth or within a few years. Intense tremor can interfere with drinking and speech functions. Sometimes the clinical picture of the pathology is supplemented by sleep and behavior disorders. The course of geniospasm is long, with age the number of episodes decreases.
Tremor is the most common abnormal movement in the neonatal period. In the first week of life, almost all children experience fine trembling, which is part of the structure of transient adaptation syndromes. Trembling of the chin is the result of an increase in neuro-reflex excitability due to the activation of stress mechanisms in response to transient hypoxia and physical exertion during childbirth.
Mild or moderate changes in the functions of the nervous system are also caused by extracerebral causes - unstable bowel function, dysmetabolic conditions (hyperbilirubinemia, hypoglycemia). In addition to trembling of the chin, such transient disorders can be manifested by tremors of the limbs, a change in behavior. After the early neonatal period, all of these symptoms disappear.
In premature babies, a small, intermittent tremor occurs due to the immaturity of the central nervous system. Among other signs, there is a decrease in motor activity, muscle hypotension, slight strabismus. Usually these changes are short-term, their duration largely depends on the degree of prematurity. Tremor can be noted when crying, due to hunger, in the phase of REM sleep, by three months should completely disappear.
If the chin trembling persists in a child a week after birth, is intense and is accompanied by other symptoms (cerebral or focal), perinatal damage to the nervous system is usually ascertained. Behind such a syndromic diagnosis lies a fairly large group of pathological conditions:
Even in the neonatal period, children with cerebral palsy are diagnosed with hyperexcitability syndrome. Early signs are general restlessness, hand and chin tremors, and increased or decreased muscle tone. The cry is weak or absent, tendon and sucking reflexes are sharply reduced, convulsions are often found. Sometimes an increase in the size of the head is detected.
In the first months of life, there is a lag in psychomotor development, the disappearance of postural reflexes of the neonatal period (labyrinthine, Magnus-Klein) is delayed. The leading defect in cerebral palsy is voluntary movement disorders - usually subtle differentiated acts involving hands are affected. As a result, the formation of age-related skills is delayed.
One of the causes of mandibular tremor in young children is progressive hydrocephalus. It occurs due to occlusion of the CSF pathways in neuroinfections (cytomegalovirus, mycoplasma), postnatal TBI, congenital vascular diseases of the brain. Critical hydrocephalus is associated with the delay in seeking specialized medical care.
The characteristic signs of hydrocephalus are an increase in the circumference and deformation of the head with a predominance of the cerebral region, bulging of the fontanelles, and an increase in the venous pattern. Moderate neurological symptoms are represented by impaired muscle tone, tremor, uneven tendon reflexes. Eye symptoms are revealed (Gref, "setting sun"), convulsions. The psychomotor development of the child is delayed, sleep, behavior, and appetite are disturbed.
Tremor of the chin in adults can develop against the background of taking antipsychotic drugs as a manifestation of neuroleptic parkinsonism. The isolated trembling of the jaw and lips that occurs in such cases is called the "rabbit" syndrome, because it resembles the chewing movements of a rodent. The disease is characterized by a gross tremor of rest and movement, except for the chin, involving the limbs and tongue.
Trembling in neuroleptic parkinsonism is a non-permanent symptom. Stability disturbances and slowness of gait are often found, but they are much less pronounced than in Parkinson's disease. Characterized by a mask-like face (hypomimia), salivation. The syndrome usually occurs 1–2 weeks after the appointment or increase in the dose of an antipsychotic, does not progress and disappears with the withdrawal of the drug.
Tremor as a visual symptom is easy to determine already during the initial examination. It is much more important to establish the cause of rhythmic chin trembling, since this affects the therapeutic strategy and prognosis. A neurologist manages to cope with such a task using additional diagnostic methods. Depending on the clinical situation, the following procedures may be prescribed:
In many cases, an examination of the fundus is necessary, echo and rheoencephalography provide some information. When conducting differential diagnosis, physiological conditions and a dangerous pathology that require immediate assistance are first excluded. Tremor in children should be distinguished from convulsive seizures, absences, myoclonus; at an older age, motor stereotypes should be taken into account.
Therapeutic tactics is determined by the nature of the underlying pathology, the symptom of which is trembling. Some conditions, such as neonatal tremor, go away on their own and do not require medical attention, while other situations require specialized care. Usually, the emphasis is on complex drug correction:
The traditional method of treating kernicterus is phototherapy, with the ineffectiveness of which practice exchange transfusion. The consequences of perinatal damage to the nervous system, cerebral palsy require complex neurorehabilitation - with physiotherapy (myostimulation, electrophoresis, reflexology), massage, exercise therapy. Special devices (orthoses) are used, classes with a speech therapist and a psychologist are recommended for children.
Radical elimination of some causes of trembling is possible only by neurosurgical means. The operation is indicated for the evacuation of the spilled blood, drainage of the ventricular spaces of the brain. In these cases, less invasive endoscopic techniques are preferred. For severe and drug-refractory tremor, deep brain stimulation or stereotaxic surgery with cryodestruction of the thalamus is used.